21 research outputs found
Identification of simple sequence repeat markers for sweetpotato weevil resistance
The development of sweetpotato [Ipomoea batatas (L.) Lam] germplasm with resistance to sweetpotato weevil (SPW) requires an understanding of the biochemical and genetic mechanisms of resistance to optimize crop resistance. The African sweetpotato landrace, âNew Kawogoâ, was reported to be moderately resistant to two species of SPW, Cylas puncticollis and Cylas brunneus. Resistance has been associated with the presence of hydroxycinnamic acids esters (HCAs), but the underlying genetic basis remains unknown. To determine the genetic basis of this resistance, a bi-parental sweetpotato population from a cross between the moderately resistant, white-fleshed âNew Kawogoâ and the highly susceptible, orange-fleshed North American variety âBeauregardâ was evaluated for SPW resistance and genotyped with simple sequence repeat (SSR) markers to identify weevil resistance loci. SPW resistance was measured on the basis of field storage root SPW damage severity and total HCA ester concentrations. Moderate broad sense heritability (H2 = 0.49) was observed for weevil resistance in the population. Mean genotype SPW severity scores ranged from 1.0 to 9.0 and 25 progeny exhibited transgressive segregation for SPW resistance. Mean genotype total HCA ester concentrations were significantly different (P < 0.0001). A weak but significant correlation (r = 0.103, P = 0.015) was observed between total HCA ester concentration and SPW severity. A total of five and seven SSR markers were associated with field SPW severity and total HCA ester concentration, respectively. Markers IBS11, IbE5 and IbJ544b showed significant association with both field and HCA-based resistance, representing potential markers for the development of SPW resistant sweetpotato cultivars
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Design and characterization of a pneumatic micro glass beads matrix sensor for soil water potential threshold control in irrigation management
Soil moisture porous matrix sensors may be good alternatives to tensiometers for measuring soilâwater matric potential (SMP) for irrigation scheduling based on soilâwater status approaches. The objective of this paper is to present and evaluate a new porous matrix sensor (IGstat) for detecting specific SMP thresholds for possible application in irrigation scheduling regulated by the SMP threshold concept. The IGstat sensor uses a non-sintered, glass bead microspheres (microGB) core and an outer ceramic cup, having larger air bubbling pressure (BP), to establish hydraulic contact with the soil. Pneumatic, optical, or electrical properties of the microGB porous medium can be then measured to infer the SMP. This paper describes and evaluates the performance of IGstat sensors for SMP threshold detection, using the pneumatic mode with a small air flow applied and air pressure monitored in the sensor tubing. Five IGstat sensors were built with different microGB diameters (15â125 ”m) having air BP varying from 6 to 40 kPa. A power function was fitted to the data, which can be used to select microGB diameters to build IGstat sensors of required air BP. The experimental setup proposed to determine the sensor BP by incremental air injection provided air BP values in good agreement with those observed in a soil evaporation experiment (average relative error of 7.6%). The sensor responses in soil, with a small air pressure applied to them, showed a sharp pressure decreases when the SMP approached the sensor air BP, decreasing to about zero for SMP equal to the sensor air BP. The proposed sensors and approach showed potential for irrigation scheduling